Method and apparatus for enhancing SE detection in mirror-based light imaging charged particle microscopes

Abstract

Apparatus include a reflector positioned adjacent to a sample location that is situated to receive a charged particle beam (CPB) along a CPB axis from a CPB focusing assembly so that the reflector is situated to receive light emitted from a sample at the sample location based on a CPB-sample interaction or a photon-sample interaction and to direct the light to a photodetector, and a steering electrode situated adjacent to the reflector so as to direct secondary charged particles emitted from the sample based on the CPB-sample interaction away from the reflector and CPB axis. Methods and systems are also disclosed.

We claim: 
     
       1. An apparatus, comprising:
 a reflector positioned adjacent to a sample location that is situated to receive a charged particle beam (CPB) passing through a reflector aperture along a CPB axis from a CPB focusing assembly so that the reflector is situated to receive light emitted from a sample at the sample location based on a CPB-sample interaction or a photon-sample interaction and to direct the light to a photodetector; and 
 a steering electrode situated adjacent to the reflector so as to direct secondary charged particles emitted from the sample based on the CPB-sample interaction away from the reflector and CPB axis. 
 
     
     
       2. The apparatus of  claim 1 , wherein the reflector is a curved reflector situated to collimate or focus the light along an optical axis. 
     
     
       3. The apparatus of  claim 2 , wherein the curved reflector is a parabolic reflector or an ellipsoidal reflector. 
     
     
       4. The apparatus of  claim 1 , further comprising a movement stage coupled to the reflector and situated to move the reflector relative to the CPB axis or sample location. 
     
     
       5. The apparatus of  claim 1 , wherein a length of the reflector includes an extension providing an additional collection angle for the light emitted from the sample and having an extension length at least in part based on the directing of the secondary charged particles with the steering electrode away from the reflector. 
     
     
       6. The apparatus of  claim 1 , further comprising a movement stage coupled to the steering electrode and situated to vary one or more of a distance and angle between the steering electrode and the reflector or CPB axis. 
     
     
       7. The apparatus of  claim 6 , wherein the steering electrode comprises an antenna electrode. 
     
     
       8. The apparatus of  claim 6 , wherein the steering electrode comprises an electrostatic plate. 
     
     
       9. The apparatus of  claim 1 , further comprising a secondary charged particle detector situated to receive the secondary charged particles emitted from the sample and directed by the steering electrode. 
     
     
       10. The apparatus of  claim 1 , further comprising the CPB focusing assembly situated to direct the CPB along the CPB axis to a focus at the sample location. 
     
     
       11. The apparatus of  claim 1 , wherein the CPB comprises an electron beam, the second charged particles comprise secondary electrons, and the light comprises cathodoluminescence. 
     
     
       12. The apparatus of  claim 11 , wherein a length of the reflector includes an extension providing an additional collection angle for the light emitted from the sample and having an extension length at least in part based on the directing of the secondary charged particle with the reflector bias. 
     
     
       13. The apparatus of  claim 1 , wherein the reflector and the steering electrode are situated to simultaneously direct the light to the photodetector and the secondary charged particles to a secondary charged particle detector. 
     
     
       14. The apparatus of  claim 1 , wherein the reflector is situated to receive a voltage so as to provide a bias that directs the secondary charged particles away from the reflector and CPB axis. 
     
     
       15. The apparatus of  claim 14 , wherein the reflector is situated to receive different voltages at different portions of the reflector. 
     
     
       16. The apparatus of  claim 15 , wherein the different portions comprise a first portion and a second portion with the first portion receiving a larger bias than the second portion, wherein the first portion is along a strong curving section adjacent to the sample location and the second voltage is along a weaker curving section adjacent to the sample location. 
     
     
       17. The apparatus of  claim 1 , further comprising a light source configured to emit a light beam to produce the photon-sample interaction. 
     
     
       18. The apparatus of  claim 17 , wherein the light emitted from the sample corresponds to a Raman emission. 
     
     
       19. A method, comprising:
 positioning a reflector adjacent to a CPB sample location situated to receive a charged particle beam (CPB) along a CPB axis from a CPB focusing assembly so that the reflector is situated to receive light emitted from the sample at the sample location based on a CPB-sample interaction or a photon-sample interaction and to direct the light to a photodetector; and 
 positioning a steering electrode adjacent to the reflector so as to direct secondary charged particles emitted from the sample based on the CPB-sample interaction away from the reflector and CPB axis. 
 
     
     
       20. The method of  claim 19 , wherein a length of the reflector includes an extension providing an additional collection angle for the light emitted from the sample and having an extension length at least in part based on the directing of the secondary charged particles with the steering electrode away from the reflector. 
     
     
       21. The method of  claim 19 , wherein the reflector is a parabolic reflector situated to collimate or focus the light along an optical axis. 
     
     
       22. The method of  claim 19 , further comprising directing the CPB to the sample;
 detecting the light with the photodetector; and 
 detecting the secondary charged particles with a charged particle detector. 
 
     
     
       23. The method of  claim 22 , wherein the CPB is an electron beam, the second charged particles are secondary electrons, and the light comprises cathodoluminescence. 
     
     
       24. A system, comprising:
 at least one processor; and 
 one or more computer-readable storage media including stored instructions that, responsive to execution by the at least one processor, cause the system to control a-voltage of a steering electrode situated adjacent to a reflector so as to direct secondary charged particles away from the reflector and a charged particle beam (CPB) axis, wherein the second charged particles are emitted from a sample at a sample location based on an interaction between a CPB propagating along a CPB axis and the sample, wherein the reflector is positioned adjacent to the sample location and the sample location is situated to receive the CPB along the CPB axis from a CPB focusing assembly so that the reflector is situated to receive light emitted from the sample based on the CPB-sample interaction or a photon-sample interaction and to direct the light to a photodetector.